When operating a vehicle, sounds coming from outside the vehicle, especially car horns, emergency vehicle sirens, and other customary warning or alarm sounds, can alert the vehicle operator to certain driving events, including an approaching emergency vehicle, another driver honking to grab the operator's attention, the sounding of an emergency warning system, or the like. In some cases, the vehicle operator may not notice or hear these sounds, even when they are loud, because the operator is preoccupied (e.g., with a phone conversation, talking to other passengers, or using a handheld device), has a volume of the vehicle audio system turned up high, or is wearing headphones or other noise-blocking device (e.g., ear plugs). In the case of hearing-impaired or deaf drivers, human detection of roadside sounds may not be an option at all.
In some instances, visual cues, such as the flashing lights of an emergency vehicle or the behavior of other drivers on the road, can alert the vehicle operator to the driving event producing the warning or alarm sounds, as an alternative or supplement to the audio cues. However, there are times when a more immediate reaction to the driving event, such as the reaction typically triggered by horns, sirens, and other audio cues, is desirable. Accordingly, there is still a need for an additional alert system in vehicles for notifying operators of sounds coming from outside the vehicle.